There are many different systems available for video projections. Such systems include, but are not necessarily limited to, color Liquid Crystal Display (LCD) projectors, Cathode Ray Tube (CRT) projectors, micro-mirror projectors and so forth. There are also back projection systems available, that project on the back of translucent or transparent material, and are viewed from the opposite direction, but they use generally the same technology as the systems already mentioned. In general, however, all of these display systems are rather expensive and have difficulty proving satisfactory light levels.
Less expensive units than those mentioned above have recently become available, mostly based on small active matrix color LCD's (AM-LCD's) or thin-film transistor LCD's (TFT-LCD's). These systems are a partial solution to the problems besetting projection display technology, but resolution and brightness are still limited, and cost compared to regular Television sets (TV's) is still rather high. The brightness availability is still marginal, so, in a living room, which will typically have large windows, daylight viewing may not be effective due to strong ambient light. Of course curtains can be closed, or a special windowless TV room can be built, but cost and ease of use suffer.
What is clearly needed are better projection systems and better methods, crossing traditional media boundaries.
One simple way to offer more brightness is to use brighter, better lamps. This allows more light to be projected. The problem, however, with brighter, more powerful lamps is that the lamps generate a lot of heat, requiring noisy high speed fans, and at the same time drastically reduce the useful life of LCD's used in such projection schemes by thermally loading the LCD's to the maximum allowable, and sometimes beyond. This is true partly because in a conventional color AM-LCD only 2-5% of light is transmitted when a cell is on, and near 0% when the LCD cell is off. This fact dictates that most light is converted into heat in the LCD.